When presented with a large population of items such as hundreds, thousands, or more items, there are many ways to present these items and many ways to select a group of these items meeting a set of criteria.
Traditionally, when going to a restaurant, the population of available food items may be displayed in categories such as, for example, appetizers, salads, entrees, desserts, side dishes. Subcategories signifying the kind of flavor, style of dish, or the main ingredient are also common. Examples of the actual values (or “items”) include beef, chicken, vegetarian, spicy, house specialties, etc. Because the size of this list is manageable, a restaurant patron typically has no problem mentally filtering through the population of menu choices to select those items to order for a meal.
Another example of a large population of items are the course offerings at a university. Courses are typically arranged in a school bulletin by department and then, within department, as introductory, upper level classes, and graduate classes. Other information such as lists of required courses for majors or concentrations are also provided. Although a little more complicated and extensive than a restaurant menu, a student can readily select those courses the student wishes to take by flipping through the categorized listings in a school bulletin.
Another example of a large population of items are those securities, stocks, mutual funds, and other investment products that may be available to an investor. Groups of securities include those listed on the New York Stock Exchange (NYSE), traded on the NASDAQ and the American Stock Exchange, and those comprising well known indices such as the Russell 2000, Standard & Poor's 500, etc. Stocks and mutual funds may be categorized by capitalization as large, middle, and small, as emerging growth, value, growth, high risk, low risk, or any combination of these and other categorizations. However, unlike using a restaurant menu or a school bulletin, it is more challenging to select from the population of securities or mutual funds those securities or mutual funds that meet a set of desired criteria, at least in part because there are many more possible values than present in a restaurant menu, and each value can be categorized by many more properties).